Nowadays, in many countries, helmets to protect motorcyclists are required when people ride in motorcycles. Thus, the development of the safety helmet design becomes more and more important. As shown in FIG. 1, the helmet ventilation device described in the previous art has two ventilation slits on the front surface so that the air can flow into the helmet. However, since the interior of the helmet is fully occupied by the head of the wearer, the air can only reach the forehead, not the entire scalp. Hence, such poor air ventilation often results in intolerable overheating of the scalp, especially in summer time. Moreover, although such ventilation slits are equipped with a device to avoid water leakage, the device usually fails to function normally. When it rains, the rain can easily leak into the helmet through the ventilation slits causing discomfort.
Based on the findings of the aforementioned drawbacks, it is therefore desirable to introduce an improved helmet ventilation device not only to provide good air ventilation and to avoid water leakage but also to make wearers more comfortable.